This invention relates to a process for stretch breaking carbon and glass filaments and using the stretch broken slivers therefrom to form a composite of either a matrix reinforced with carbon fibers or a matrix reinforced with glass fibers.
Composite sheets of either continuous filament carbon fiber reinforced resin or continuous filament glass fiber reinforced resin have been made. One technique is to prepare a warp of filaments as by winding on a frame, impregnating them with resins and hot pressing to form a thin flat sheet which is cut from the frame. Several such sheets are then cross lapped and again hot pressed to form the final reinforced composite product. Such products have high strength and stiffness.
Problems occur when attempts are made to produce deep drawn three dimensional articles by hot pressing continuous carbon or glass filament containing resin sheets. The articles in many instances exhibit uneven areas and wrinkles. The use of staple carbon or glass fibers as reinforcement substantially overcomes the above-stated problems but at a great sacrifice to strength and stiffness.
In a similar situation involving P-aramid fibers, a solution to the aforementioned problem was the use of certain stretch broken P-aramid fibers as disclosed by Fish and Lauterbach in U.S. Pat. No. 4,552,805. However, because carbon and glass filaments exhibit little or no cohesive capability when processed according to known stretch-breaking processes, slivers of carbon or glass fibers have not been able to be formed by these known processes.
The present invention permits forming cohesive slivers of stretch broken filaments of carbon and glass for use in forming a composite carbon or glass fiber reinforced resin useful for deep drawing purposes with little sacrifice of strength and stiffness.